This invention relates to an image pickup apparatus and an image pickup method.
A solid-state image pickup device photoelectrically converts light incoming to a light receiving face thereof to produce charge and cumulatively stores the charge in accordance with a charge storage time period set in advance and then outputs an image pickup signal corresponding to the stored character. A solid-state image pickup device of the type described includes pixels arranged in rows and columns, that is, in a matrix, to perform photoelectric conversion.
Where the solid-state image pickup device is formed from CMOS sensors, reading out of image pickup signals from the individual pixels is performed either such that the image pickup signals are read out successively in a unit of a row (line) in which the pixels are arranged or in a focal plane fashion wherein the image pickup signals are read out successively in a unit of a single pixel.
It is known that, if an image pickup apparatus having such CMOS sensors as described above is used under light emitted from a light source using a commercial power supply, then when the charge storage time of the CMOS sensors is not equal to an integral number of times the cycle of variation of the luminosity of light of the light source, noise in the form of stripes which extend in a horizontal direction appears on a screen (frame) formed from an image pickup signal outputted from the CMOS sensors.
An image pickup apparatus which eliminates such a disadvantage as just described has been proposed, for example, in Japanese Patent Laid-Open No. 2003-333423. The image pickup apparatus includes a light amount detector for detecting cyclic variation of the luminosity of light of a light source, and an A/D converter for converting a detection signal of the light amount detector into a digital signal. The image pickup apparatus further includes a correction circuit for correcting the image pickup signal outputted from CMOS sensors and converted into a digital signal based on a cycle of variation of the detection signal supplied from the A/D converter.
The correction circuit includes a gain amplifier (multiplier) and adjusts the amplification factor of the gain amplifier in response to the detection signal supplied thereto from the A/D converter to correct the level of the image pickup signal.